Pancreatic cancer accounts for approximately 2% of all new cancer cases in the United States, but almost 6% of cancer deaths. This reflects the very poor prognosis of this disease, and the current lack of effective therapies. As a consequence, there is a major need to explore new treatments, including gene therapy. Oncolytic, conditionally-replicating adenoviruses (CRADs) are presently being explored for their potential efficacy in the context of pancreatic cancer. The current generation of oncolytic CRADs are based on viruses with specific modifications in the E1 locus, including deletion of the E1B gene or transcriptionally-targeted, tumor-cell specific expression of the E1A gene. While initial clinical studies of oncolytic CRADs have shown that these vectors are generally safe and well tolerated, additional improvements will be necessary to make oncolytic CRADs more effective. In this proposal, we will generate new oncolytic CRADs using an entirely novel strategy. These adenovirus vectors will contain mutant DNA polymerases with a high functional dNTP requirement, and are expected to replicate selectively in tumor cells as a result. We anticipate that a powerful opportunity for synergy may exist, by combining our polymerase-based strategy with current E1-locus based oncolytic approaches - resulting in a new generation of CRADs that may have improved safety and efficacy. Overall, these experiments are expected to facilitate the development of novel approaches to the development of improved oncolytic adenovirus vectors for treatment of pancreatic cancer. It is hoped that these improvements will provide safer and more effective treatments for this deadly disease. Pancreatic cancer accounts for approximately 2% of all new cancer cases in the United States (32,180 in total, for 2005), but almost 6% of cancer deaths (31,800 in total, for 2005). Thus, pancreatic cancer (PC) is not only common, but it is also associated with a very poor prognosis. This makes PC an important potential target for new treatment approaches, including gene therapy. This application proposes to develop a novel gene therapy approach employing oncolytic adenovirus replicating specifically in cancer cells. [unreadable] [unreadable] [unreadable]